Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Sully H.W. Bush Instagram)

President George H.W. Bush with his service dog Sully in 2018

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Sully H.W. Bush Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Sully H.W. Bush Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Sully H.W. Bush Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully as a puppy (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

Sully looked somber and sad as he waited to board Special Air Mission 41 for his master's final journey to our nation's capital. (Getty Images)

Sully looked sad and somber as he escorted his master's casket out of the Lewis & Sons funeral home.

Images from Monday morning and the state funeral for President George H. W. Bush -- family at the funeral home, Secret Service honorary pallbearers, and boarding "Special Air Mission 41" at Ellington Field.

Late President George H.W. Bush has arrived in Washington D.C. ahead of memorial services.

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Sully H.W. Bush Instagram)

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President George H.W. Bush with his service dog Sully in 2018

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Sully H.W. Bush Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Sully H.W. Bush Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Sully H.W. Bush Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully as a puppy (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully H.W. Bush brought countless hours of happiness to George H.W. Bush after the death of his beloved wife Barbara. (Instagram)

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Sully looked somber and sad as he waited to board Special Air Mission 41 for his master's final journey to our nation's capital. (Getty Images)

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Sully looked sad and somber as he escorted his master's casket out of the Lewis & Sons funeral home.

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Images from Monday morning and the state funeral for President George H. W. Bush -- family at the funeral home, Secret Service honorary pallbearers, and boarding "Special Air Mission 41" at Ellington Field.

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Late President George H.W. Bush has arrived in Washington D.C. ahead of memorial services.

Bush’s longtime spokesman, Jim McGrath, tweeted a photo the service dog lying in front of the casket. The caption read, “Mission complete.”

It's full of photos of the popular dog, frolicking at the beach, playing with other dogs and lying beside President Bush's wheelchair.

“The emotional connection between the 2 must have been incredible,” says Paul Buescher, Executive Director of the Houston-based non-profit, “A Cause to Give Us Paws,” which trains service dogs.

Bush 41 had a form of Parkinson’s Disease, which caused difficulty with balance, among other symptoms. Sully could open doors, pick things up and summon help, if needed. Sully even helped the president vote last month, in the midterm elections.

“Sully looks to be an amazing dog,” adds Buescher.

Sully was named after Captain Chesley “Sully” Sullenberger, the pilot who safely landed a damaged passenger jet on New York City’s Hudson River, in 2009.

President Bush, a Navy pilot during World War II, tweeted about Sully when he first got him in June, calling him “beautifully trained.”

At the president's request, Sully's next mission will be working at Walter Reed National Military Medical Center.

"As much as our family is going to miss this dog, we're comforted to know he'll bring the same joy to his new home, Walter Reed, that he brought to 41,” President George W. Bush wrote on Instagram Sunday night.